1. Field
Apparatus and methods described in this document relate to electronic circuit designs. More specifically, the apparatus and methods relate to switched capacitor integration and summing circuits.
2. Background
Some electronic devices include switched capacitor circuits implementing both integration and signal-summing functions. In particular, sigma-delta modulators or converters may use switched capacitor integrators followed by switched capacitor summers. Sigma-delta modulators may be employed, for example, to convert an intermediate frequency (IF) signal to a baseband frequency signal, in order to meet dynamic range requirements for digital signal processing, and to provide improved adaptability and programmability to receiver circuitry. In these and other applications, the advantages of sigma-delta modulators include high dynamic range, which is often needed to distinguish a small desired signal from blockers and interferers. Sigma-delta modulators shape the quantization noise out-of-band, and allow combining decimation filtering with selective digital filtering and IF mixing to attenuate both the quantization noise and neighboring blockers. In addition, the ability to select different sampling rates in the sigma-delta modulator architecture allows a single device to be adapted to different requirements, for example, the requirements imposed by multiple RF standards. Moreover, the use of higher sampling rates and complex digital signal processing allow sigma-delta converters to exhibit relatively low sensitivity to interfering analog signals.
Size, weight, power consumption, speed, and production costs loom large in designing electronic equipment, and especially portable battery-operated electronic equipment such as wireless access terminals. Therefore, there is a need in the art to reduce the power consumption of electronic equipment, including sigma-delta modulators and other devices that include integrators and summers. There is also a need in the art to decrease size and weight of electronic equipment, including sigma-delta modulators and other devices that include integrators and summers. There is a further need in the art to lower the cost of manufacturing electronic equipment, including sigma-delta modulators and other devices that include integrators and summers. There is still another need in the art to increase the operating speed of electronic equipment, including sigma-delta modulators and other devices that include integrators and summers.